Enhanced dielectric and piezoelectric properties of BNT-KNNG piezoelectric ceramics

Abstract The structural, morphological and electric properties of (1- x ) Bi 0.5 Na 0.5 TiO 3 – x K 0.5 Na 0.5 NbO 3  + 1 wt. % Gd 2 O 3 (BNT-KNNG; x  = 0–0.02) ceramics were investigated in detail. XRD studies revealed the rhombohedral phase, which is also confirmed by HRTEM. The diffuse phase transition of BNT-KNNG samples exhibited a relaxor behaviour supported by modified Curie Weiss law and Vogel–Fulcher law. The AC-Conductivity of BNT-KNNG ceramics in terms of hopping length, hopping energy and density of states across the Fermi level was analyzed by Mott's variable range hopping mechanism. The addition of KNNG effectively reduced grain size, transition temperature, leakage current and improved dielectric ( e′  = 1074 and tan δ  = 0.059 @ 1 kHz) and piezoelectric properties; electromechanical coupling factors ( k 33 , k 31 , k t  ∼ 48% and k p  = 53%), and piezoelectric constants ( d 33  = 108 pC/N and g 33  = 1.14 × 10 −2 Vm/N) are observed for x  = 0.01 sample, which is a potential candidate for high power electromechanical applications.